Composite membrane

Abstract

A composite membrane excelling in organic solvent resistance, heat resistance and organic vapor resistance is disclosed. The composite membrane of the present invention comprises a porous membrane including as a major constituent a polymer having a repeating unit represented by the formula (I) --Ph--S--Ph--SO.sub.2).sub.n (I) (wherein Ph represents phenyl group, n represents a natural number) and an active layer formed on said porous membrane. The composite membrane of the present invention may be used as a composite membrane for pervaporation, gas separation membrane and as a reverse osmosis membrane.

We claim: 
     
       1. A composite membrane comprising a porous membrane including as a major constituent a polymer having a repeating unit represented by the formula (I)   --Ph--S--Ph--SO.sub.2).sub.n                               (I)     (wherein Ph represents phenyl group, n represents a natural number) and an active layer formed on said porous membrane.   
     
     
       2. The composite membrane of claim 1, wherein said active layer is made of a material having pervaporation separation property. 
     
     
       3. The composition membrane of claim 2, wherein said material having pervaporation separation property is selected from the group consisting of polydimethylsiloxane, polytrimethylsilylpropine-1, chitosan, alginic acid and polyvinyl alcohol. 
     
     
       4. The composite membrane of claim 1, wherein said active layer is made of a material having reverse osmotic property. 
     
     
       5. The composite membrane of claim 4, wherein said material having reverse osmotic property is a cross-linked polyamide prepared by interfacial polycondensation. 
     
     
       6. The composite membrane of claim 5, wherein said cross-linked polyamide comprises as a major constituent a cross-linked aromatic polyamide or a cross-linked piperazine polyamide. 
     
     
       7. The composite membrane of claim 1, wherein said active layer is made of a material having gas separation property. 
     
     
       8. The composite membrane of claim 7, wherein said material having gas separation property is selected from the group consisting of polydimethylsiloxane, polyolefins and polyimides. 
     
     
       9. The composite membrane of claim 1, wherein the composite membrane is in the form of a flat membrane, and wherein the composite membrane further comprises a fabric or a non-woven fabric on which said composite membrane is laminated, which fabric or non-woven fabric being made of a polymer selected from the group consisting of polyesters, polyamides, polyethylene, polypropylene and polyphenylenesulfide. 
     
     
       10. A composite membrane comprising a porous membrane prepared by oxidizing a porous membrane including as a major constituent a polymer having a repeating unit represented by the formula (I)   --Ph--S--Ph--SO.sub.2).sub.n                               (I)     (wherein Ph represents a phenyl group and n represents a natural number) and an active layer formed on said porous membrane.   
     
     
       11. The composite membrane of claim 10, wherein the oxidation of the porous membrane is carried out by immersing the porous membrane in an oxidizer selected from the group consisting of peracetic acid, chloroperbenzoic acid and tetrabutylammonium hypochlorite.